Many people are concerned with the degree of pigmentation of their skin. For example, people with age spots or freckles may wish such pigmented spots to be less pronounced. Others may wish to reduce the skin darkening caused by exposure to sunlight or to lighten their natural skin color. To meet this need, many attempts have been made to develop products that reduce the pigment production in the melanocytes. However, the substances identified thus far tend to have either low efficacy or undesirable side effects, such as, for example, toxicity or skin irritation. Therefore, there is a continuing need for new cosmetic skin lightening agents, with improved overall effectiveness.
For example, certain resorcinol derivatives, particularly 4-substituted resorcinol derivatives, are useful in cosmetic compositions for skin lightening benefits, as disclosed in Hu et al., U.S. Pat. No. 6,132,740; Bradley, et al., U.S. Pat. Nos. 6,504,037 and 6,861,564; Japanese published patent applications JP 2001-010925 and JP2000-327557; and Harichian et al., U.S. Pat. No. 6,852,310.
Applicants have now discovered that N-acylbenzothiazolones, particularly 3-propionylbenzothiazol-2-one, and derivative compounds deliver skin lightening benefits. The general chemical formulas and structures of these compounds are discussed in more detail herein below. The 3-propionylbenzothiazol-2-one and derivative compounds have been found to be cosmetically effective and possibly less irritating to the skin. These compounds of the present invention have not been used in cosmetics, nor have they been used, specifically, for lightening skin.
The synthesis of 3-propionylbenzothiazol-2-one is described in Ucar, et al., “Fries-Like’ Rearrangement: a Novel and Efficient Method for the Synthesis of 6-Acyl-2(3H)-benzoxazolones and 6-Acyl-2(3H)-benzothiazolones,” Tetrahedron, 54:1763-1771 (1998). Ucar, et al., “Synthesis and Anticonvulsant Activity of 2(3H)-Benzoxaxolone and 2(3H)-benzothiazolone Derivatives,” J. Med. Chem. 41:1138-1145 (1998) discloses evaluation of 2(3H)-benzothiazolone derivatives for anticonvulsant activity.